1. Field of the Invention
This invention concerns a rotation mechanism which provides a couple for, and thus rotates, an annular ring such as that used to drive the fins in a rotation mechanism for rotating the adjustable fins of a gas turbine.
2. Description of the Invention
A rotation apparatus for varying the angle of and rotating the static fins in a gas turbine is shown in FIG. 1. (This figure is a preferred embodiment of the present invention and not an example of the prior art.) Rotary shafts 2a of (static) fins 2, which are rotatably mounted in compartment 1, are connected to rotation ring 4 through levers 3. When the rotation ring 4 is rotated, the fins 2 rotate as indicated by the arrows in FIG. 1.
The rotation ring 4 has a number of supports 6 on it which are supported by washers 5 on the surface of compartment 1 when the ring rotates.
Although only a single fin 2 is shown in FIG. 1, the relevant gas turbine in fact has a number of such fins at regular intervals around the periphery of compartment 1. When the rotation ring 4 rotates, all the fins 2 rotate simultaneously.
An example of a rotation mechanism for rotating the ring which drives the fins in a gas turbine is a single link 10 which rotates rotation ring 4, as provided in Japanese Patent Publication (Kokai) Showa 59-7708. With this design, the force which rotates rotation ring 4 is balanced with the opposing force to supports 6 on rotation ring 4. However, in this rotation mechanism, the radius of rotary shaft 2a of fin 2, which is supported in the compartment 1, and the point of action of the force are in a ratio of nearly 1:1. Thus the drag torque due to friction will be considerable.
Further, the radius of the rotation ring 4 is greater than that of compartment 1, and consequently the ring is more prone to warping. All of the above-mentioned factors have an adverse effect on the smooth operation of the rotation mechanism which rotates rotation ring 4.
The rotation devices which the prior art provides to solve the problems discussed above are the rotation mechanisms pictured in FIGS. 9, 10 and 11, which rotate rotation ring 4 through a couple.
FIGS. 9 and 10 show a prior art rotation mechanism for rotating the ring which drives the rotation of the fins.
In FIGS. 9 and 10, 4 is the rotation ring which rotates fins 2 as shown in FIG. 1.
Pins 51 and 52 are inserted through holes on opposite sides of the outer edge of the rotation ring 4. One end of each of the follower links 10 and 11 is rotatably mounted to the pins 51 and 52, respectively.
Operating lever 17 is rotatably mounted through operating shaft 18 to bracket 43, which is fixed to the top of stage 40 (See FIG. 1).
Pin 200 is inserted through one end of the lever 17. One end of each of links 14 and 15 is rotatably mounted in the pin 200, as is shown in FIG. 10.
To the left and right of the bracket 43 are brackets 41 and 42, both of which are also fixed to the stage 40. L-shaped levers 12 and 13, which face in opposite directions, are rotatably mounted to brackets 41 and 42, respectively, through lever shafts 56 and 55.
The other end of link 14 is connected through pin 58, in such a way that the link is free to rotate, to one end of L-shaped lever 12, the lever on the right side of the rotation mechanism. The other end of link 15 is connected through pin 57, in such a way that the link is free to rotate, to one end of lever 13, the lever on the left side of the rotation mechanism.
The other end of the L-shaped lever 12 is connected through pin 53 to the free end of follower link 10. The other end of the L-shaped lever 13 is connected through pin 54 to the free end of follower link 11.
With this sort of rotation mechanism for the rotation ring, a drive means, such as a servo hydraulic cylinder (not shown), rotates operating lever 17, through the mediation of the operating shaft 18, in the direction shown by arrow Z1 in FIG. 9. When this happens, links 14 and 15 move horizontally to the right, as indicated by arrow Z2. L-shaped lever 12 rotates counterclockwise on shaft 56, as shown by arrow Z3. L-shaped lever 13 also rotates counterclockwise on its lever shaft 55, as shown by arrow Z4. Link 10 on the right side moves upward as shown by arrow Z5; link 11 on the left side moves downward as shown by arrow Z6.
Thus the links 10 and 11 provide a couple to rotation ring 4, which rotates counterclockwise as shown by arrow Z7. As the rotation ring 4 rotates, fins 2 are rotated in the specified direction.
In the prior art design shown in FIGS. 9 and 10, links 10 and 11, which drive rotation ring 4, are connected to opposite sides of the rotation ring. The forces which operate on rotation ring 4 are coupled. Because the load which is concentrated at a single point diminishes, the resultant force which acts on support 6 approaches zero. There is less warping and friction, the rotation mechanism operates smoothly, and the operating force itself decreases.
In the prior art design shown in FIGS. 9 and 10, however, links 14 and 15 are directly attached to a single pin 200, which is mounted to one end of operating lever 17, and so they move left and right. Thus links 14 and 15 have very little freedom and must move at an excessive speed, which may result in increased frictional drag. Also, a large operating force is needed to drive rotation ring 4 through the links 14 and 15. The configuration makes it difficult to eliminate the effects of warping due to the load on links 14 and 15 and the levers connected to them or due to the thermal expansion of these components, which in turn may result in excessive operating force or defective operation.
The prior art device shown in FIG. 11 is a rotation mechanism for driving the rotation of the rotation ring 4 using a driving means such as a servo hydraulic cylinder.
In this design, two cylinders, namely servo oil hydraulic cylinder 60 and slave cylinder 61, are arranged symmetrically 180.degree. apart and connected by pipes 64 and 65. The free end of piston rod 66 of servo oil hydraulic cylinder 60 is connected to pin 51 on the outer edge of rotation ring 4. The free end of piston rod 67 of slave cylinder 61 is connected to pin 52, which is 180- opposite pin 51 on the outer edge of rotation ring 4.
When piston 62 of cylinder 60 is hydraulically driven, piston rod 66 moves in the direction indicated by arrow Y.sub.1 and piston rod 67 of slave cylinder 61 moves in the direction indicated by arrow Y.sub.2. The couple generated in this way rotates rotation ring 4 in the direction indicated by arrow Y.sub.3.
If a turbine has multiple rows of fins to be driven, a rotation mechanism using a servo hydraulic cylinder as in the prior art device pictured in FIG. 11 will require a set of hydraulic drive components including a servo hydraulic cylinder 60 and a slave cylinder 61 for each row. This drives up the parts count and increases the cost of the device. Furthermore, the relative forces between the cylinder equipped with a pilot relay (servo hydraulic cylinder 60) and slave cylinder 61 may be unbalanced so that it becomes impossible to achieve the required operating force.